Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S5/00—Semiconductor lasers
  • H01S5/50—Amplifier structures not provided for in groups H01S5/02 - H01S5/30
  • H01S5/5036—Amplifier structures not provided for in groups H01S5/02 - H01S5/30 the arrangement being polarisation-selective
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S5/00—Semiconductor lasers
  • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
  • H01S5/068—Stabilisation of laser output parameters
  • H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S5/00—Semiconductor lasers
  • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
  • H01S5/4025—Array arrangements, e.g. constituted by discrete laser diodes or laser bar
  • H01S5/4087—Array arrangements, e.g. constituted by discrete laser diodes or laser bar emitting more than one wavelength
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S5/00—Semiconductor lasers
  • H01S5/50—Amplifier structures not provided for in groups H01S5/02 - H01S5/30
  • H01S5/5009—Amplifier structures not provided for in groups H01S5/02 - H01S5/30 the arrangement being polarisation-insensitive
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S5/00—Semiconductor lasers
  • H01S5/50—Amplifier structures not provided for in groups H01S5/02 - H01S5/30
  • H01S5/5027—Concatenated amplifiers, i.e. amplifiers in series or cascaded
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S5/00—Semiconductor lasers
  • H01S5/50—Amplifier structures not provided for in groups H01S5/02 - H01S5/30
  • H01S5/5045—Amplifier structures not provided for in groups H01S5/02 - H01S5/30 the arrangement having a frequency filtering function
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
  • H04B10/29—Repeaters
  • H04B10/291—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form
  • H04B10/2912—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form characterised by the medium used for amplification or processing
  • H04B10/2914—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form characterised by the medium used for amplification or processing using lumped semiconductor optical amplifiers [SOA]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
  • H04B10/29—Repeaters
  • H04B10/291—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form
  • H04B10/293—Signal power control
  • H04B10/294—Signal power control in a multiwavelength system, e.g. gain equalisation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J14/00—Optical multiplex systems
  • H04J14/02—Wavelength-division multiplex systems
  • H04J14/0221—Power control, e.g. to keep the total optical power constant
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J14/00—Optical multiplex systems
  • H04J14/06—Polarisation multiplex systems
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S2301/00—Functional characteristics
  • H01S2301/04—Gain spectral shaping, flattening
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S5/00—Semiconductor lasers
  • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
  • H01S5/4025—Array arrangements, e.g. constituted by discrete laser diodes or laser bar
  • H01S5/4031—Edge-emitting structures

Definitions

• the present invention relates to Wavelength Division Multiplexing (or WDM) transmission systems, and more precisely to amplification devices arranged for amplifying optical signals in such WDM transmission systems.
• WDM Wavelength Division Multiplexing
• OFDM orthogonal frequency-division multiplexing
• Nyquist pulse shaping techniques Unfortunately, this solution must be limited to a channel spacing equal to the symbol rate in order to avoid drastic linear crosstalk issue.
• an object of this invention is to improve the situation, and notably to allow increasing the optical bandwidth in WDM transmission.
• an amplification device comprises:
• first splitting element arranged for splitting an input optical signal in first and second optical signals having respectively first and second polarization modes
• first and second amplification stages each comprising first and second polarized semiconductor optical amplifiers (or SOAs) arranged for amplifying respectively the first and second optical signals as a function of driving currents,
• control means arranged for producing the driving currents as a function of information representative of powers of the first and second optical signals at least before the first and second polarized SOAs of each amplification stage and of a targeted power of the output optical signal.
• the amplification device may include additional characteristics considered separately or combined, and notably:
• the first and second polarized SOAs of each amplification stage may be arranged for amplifying optical signals having the first polarization mode.
• it may further comprise a first transformation element arranged for transforming the second polarization mode of the second optical signal in the first polarization mode before the second polarized SOA of the first amplification stage, and a second transformation element arranged for transforming the first polarization mode of the first optical signal in the second polarization mode after the first polarized SOA of the second amplification stage, so that the first combination element combines the first optical signal amplified, having the second polarization mode and outputted by the second amplification stage with the second optical signal amplified, having the first polarization mode and outputted by the second amplification stage to produce the output optical signal;
• the first transformation element and/or the second transformation element may comprise a waveplate
• first and second micro-lenses located respectively just before and just after the first polarized SOA of each amplification stage, and third and fourth micro-lenses located respectively just before and just after the second polarized SOA of each amplification stage;
• • its intermediate processing stage may comprise a) a first variable optical attenuator arranged for compensating, on the first optical signal, a tilt of the optical gain bandwidth of the first polarized SOA of the first amplification stage as a function of a driving current, b) a first gain flattening filter arranged for compensating, on the first optical signal, ripples of the optical gain bandwidth of the first polarized SOA of the first amplification stage as a function of a driving current, c) a second variable optical attenuator arranged for compensating, on the second optical signal, a tilt of the optical gain bandwidth of the second polarized SOA of the first amplification stage as a function of a driving current, and d) a second gain flattening filter arranged for compensating, on the second optical signal, ripples of the optical gain bandwidth of the second polarized SOA of the first amplification stage as a function of a driving current;
• its intermediate processing stage may comprise a) a second combination element arranged for combining the first and second amplified optical signals outputted by the first amplification stage to produce an intermediate optical signal, b) a variable optical attenuator arranged for compensating, on this intermediate optical signal, a tilt of the optical gain bandwidth of the first stage as a function of a driving current, c) a gain flattening filter arranged for compensating, on this intermediate optical signal, ripples of the first amplification stage as a function of a driving current, and d) a second splitting element arranged for splitting the intermediate optical signal, processed by the variable optical attenuator and gain flattening filter, in first and second optical signals having respectively the first and second polarization modes; its intermediate processing stage may further comprise a third transformation element arranged for transforming the first polarization mode of the first optical signal in the second polarization mode before the second combination element, and a fourth transformation element arranged for transforming the second polarization mode of the second optical signal in the first
• the third transformation element and/or the fourth transformation element may comprise a waveplate
• amplification stage it may further comprise, just before each amplification stage, a) a first extracting element arranged for taking a first predefined percentage of the power of the first optical signal before the first polarized SOA, b) a first photodiode arranged for producing a first information representative of the power taken from the first optical signal before the first polarized SOA for the control means, c) a second extracting element arranged for taking a second predefined percentage of the power of the second optical signal before the second polarized SOA, and d) a second photodiode arranged for producing a second information representative of the power taken from the second optical signal before the second polarized SOA for the control means;
• control means may be arranged for producing the driving currents as a function of information representative of powers of the first and second optical signals before and after the first and second polarized SOAs of each amplification stage and of the targeted power of the output optical signal;
• it may further comprise, after each amplification stage, a) a third extracting element arranged for taking a third predefined percentage of the power of the first optical signal after the first polarized SOA, b) a third photodiode arranged for producing a third information representative of the power taken from the first optical signal after the first polarized SOA for the control means, c) a fourth extracting element arranged for taking a fourth predefined percentage of the power of the second optical signal after the second polarized SOA, and d) a fourth photodiode arranged for producing a fourth information representative of the power taken from the second optical signal after the second polarized SOA for the control means;
• the first polarization mode may be a transverse electric (or TE) mode and the second polarization mode may be a transverse magnetic (or TM) mode;
• each splitting element and/or each combination element may comprise a birefringent material
• control means may be arranged for determining the driving currents from stored data establishing a correspondence between information representative of powers and driving currents;
• FIG. 2 schematically illustrates in a diagram an example of evolution of the optical power outputted by a polarized SOA as a function of the wavelength in nanometer (nm);
• FIG. 3 schematically and functionally illustrates a second example of embodiment of an amplification device according to the invention.
• FIG. 4 schematically and functionally illustrates a part of a third example of embodiment of an amplification device according to the invention.
• an amplification device 1 intended for amplifying input optical signals in a Wavelength Division Multiplexing (or WDM) transmission system.
• an amplification device 1 comprises at least a first splitting element 2, first 3i and second 3 2 amplification stages, an intermediate processing stage 4, a first combination element 6, and a control means 6.
• the first splitting element 2 is arranged (or configured) for splitting an input optical signal Si n in first and second optical signals having respectively first and second polarization modes. As illustrated, this input optical signal S in is provided by a first optical fiber link 7 of a WDM transmission system, which is connected to an input of the amplification device 1 .
• the first splitting element 2 may be a polarization beam splitter which may be realized by using a birefringent material that is capable of physically splitting the input optical signal S in in first and second optical signals in order to deliver them respectively onto distant first and second outputs.
• the birefringent material may be a crystal quartz.
• the first polarization mode may be a transverse electric (or TE) mode and the second polarization mode may be a transverse magnetic (or TM) mode.
• TE transverse electric
• TM transverse magnetic
• the reverse situation may be envisaged (i.e. a first polarization mode that is a TM mode and a second polarization mode that is a TE mode) if the amplifier is designed and/or positioned to amplify TM mode.
• TM transverse magnetic
• polarized SOA a SOA arranged for optimally amplifying an optical signal having a predefined polarization mode.
• This type of SOA, optimized for a predefined polarization mode, may be designed to exhibit a very large gain bandwidth.
• FIG. 2 illustrates an example of evolution of the optical power outputted by a polarized SOA with a very large gain bandwidth as a function of the wavelength in nanometer (nm).
• the gain bandwidth is larger than 120 nm, which represents a threefold increase of optical gain bandwidth with respect to commonly used EDFAs.
• each amplification stage 3 may be an integrated component that is secured to a small plate (or board) 10 and in two subparts of which are respectively defined a first SOA 8, and a second SOA 9,.
• the first 3i and second 3 2 amplification stages may define a single integrated component 1 1 that is secured to a small plate (or board) 10 and in four sub-parts of which are respectively defined the two first SOAs 8, and the two second SOAs 9i.
• the use of singly polarized SOAs 8 1 and 9i in the first amplification stage 3i may enable achieving a very large optical bandwidth with high gain, a high output power and a low noise figure.
• the second amplification stage 3 2 one may use singly polarized SOAs 8 2 and 9 2 that enable achieving a very large optical bandwidth with high saturation output power and low gain, so that a large range of output power can be covered while managing the gain flatness.
• the intermediate processing stage 4 is inserted between the first 3i and second 3 2 amplification stages. It is arranged for compensating chosen optical characteristics of the optical gain bandwidth of the first amplification stage 3i as a function of other driving currents 13, (or I3) and I4, (or I4).
• this intermediate processing stage 4 is secured to the small plate (or board) 1 0.
• the intermediate processing stage 4 comprises a first variable optical attenuator 12 1 ; a first gain flattening filter 13i , a second variable optical attenuator 1 2 2 , and a second gain flattening filter 13 2 .
• variable optical attenuators or VOAs
• GFFs gain flattening filters
• the first variable optical attenuator (or VOA) 12 ! is arranged for compensating, on the first optical signal, a tilt of the optical gain bandwidth of the first polarized SOA 8 1 of the first amplification stage 3i as a function of a driving current I3i .
• the tilt is an example of chosen optical characteristics of the optical gain bandwidth that can be compensated.
• the first gain flattening filter 1 3i is arranged for compensating, on the first optical signal, ripples of the optical gain bandwidth of the first polarized SOA 8i of the first amplification stage 3i as a function of a driving current 1 ⁇ 4-[ .
• Ripples are another example of chosen optical characteristics of the optical gain bandwidth that can be compensated.
• the second variable optical attenuator (or VOA) 12 2 is arranged for compensating, on the second optical signal, a tilt of the optical gain bandwidth of the second polarized SOA 9i of the first amplification stage 3i as a function of a driving current I3 2 .
• the second gain flattening filter 13 2 is arranged for compensating, on the second optical signal, ripples of the optical gain bandwidth of the second polarized SOA 9i of the first amplification stage 3i as a function of a driving current I4 2 .
• each variable optical attenuator 12, and each gain flattening filter 1 3 are dedicated to the polarization of the modes of the optical signals they receive respectively. This may also allow minimizing polarization dependent gain between the two paths of the amplification device 1 .
• each variable optical attenuator 12 is located upward the associated gain flattening filter 13,. But this is not mandatory. Indeed, each variable optical attenuator 12, could be located downward the associated gain flattening filter 13,.
• the intermediate processing stage 4 comprises a single variable optical attenuator 12', a single gain flattening filter 13', a second combination element 14, and a second splitting element 1 5.
• the second combination element 14 is arranged for combining the first and second amplified optical signals outputted by the first and second outputs of the first amplification stage 3i to produce an intermediate optical signal.
• this second combination element 14 may be a polarization beam combiner, which may be realized by using a birefringent material that is capable of combining the first and second amplified optical signals it receives onto distant first and second inputs in order to deliver an intermediate optical signal.
• the birefringent material may be a crystal quartz.
• variable optical attenuator 12' is arranged for compensating, on this intermediate optical signal, the tilt of the optical gain bandwidth of the first stage 3i as a function of a driving current I3.
• the gain flattening filter 13' is arranged for compensating, on the intermediate optical signal, ripples of the first amplification stage 3i as a function of a driving current I4. [40] So, in this example the variable optical attenuator 12' and the gain flattening filter 13' are not dependent from the polarization.
• variable optical attenuator 12' is located upward the gain flattening filter 1 3'. But this is not mandatory. Indeed, the variable optical attenuator 12' could be located downward the gain flattening filter 13'.
• the second splitting element 15 is arranged for splitting the intermediate optical signal, processed by the variable optical attenuator 12' and gain flattening filter 13', in the first and second optical signals having respectively the first and second polarization modes.
• this second splitting element 15 may be a polarization beam splitter which may be realized by using a birefringent material that is capable of physically splitting the intermediate optical signal in first and second optical signals in order to deliver them respectively onto distant first and second outputs.
• the birefringent material may be a crystal quartz.
• the first combination element 5 is arranged for combining the first and second amplified optical signals (outputted by the first and second outputs of the second amplification stage 3 2 ) to produce an output optical signal S ou t- As illustrated, this output optical signal S ou t feeds a second optical fiber link 1 6 of the WDM transmission system, which is connected to an output of the amplification device 1 .
• the first combination element 5 may be a polarization beam combiner, which may be realized by using a birefringent material that is capable of combining the first and second amplified optical signals it receives onto distant first and second inputs in order to deliver an output optical signal S ou t-
• the birefringent material may be a crystal quartz.
• the first splitting element 2 and the first combination element 5 are secured to the small plate (or board) 10.
• the amplification device 1 preferably comprises further at least a first micro-lens 17, located just before each first polarized SOA 8,, a second micro-lens 18, located just after the first polarized SOA 8,, a third micro-lens 19, located just before the second polarized SOA 9,, and a fourth micro-lens 20, located just after the second polarized SOA 9,.
• These micro-lenses 17,-20 allow improving light coupling between elements.
• micro-lenses 17,-20 are secured to the small plate (or board) 10.
• the control means 6 is arranged for producing all the driving currents M i, 12,, I3i (ou I3) et I4, (ou I4) as a function of information representative of powers of at least the first and second optical signals at least before the first 8, and second 9, polarized SOAs and of a targeted power of the output optical signal S out - So, it aims at controlling automatically the respective amplification levels of the first 8, and second 9, polarized SOAs of each amplification stage 3, so that the output optical signal S out be approximately equal to the targeted power (i.e. equal to the latter with a predefined tolerance).
• the control means 6 is preferably made of a combination of hardware and software modules, by means of a microcontroller or a central processing unit (CPU), for instance.
• the first 8, and second 9, polarized SOAs of each amplification stage 3, are preferably arranged for amplifying optical signals having the first polarization mode (and preferably the TE mode).
• the amplification device 1 must further comprise first 21 and second 22 transformation elements to allow a combination of first and second optical signals with different polarization modes by the first combination element 5, as illustrated in the non-limiting examples of Figures 1 , 3 and 4.
• the first transformation element 21 is arranged for transforming the second polarization mode of the second optical signal (provided by the second output of the first splitting element 2) in the first polarization mode. So, it is located before the second polarized SOA 9i of the first amplification stage 3i . It should be understood that this transformation consists in a rotation from the second polarization mode to the first polarization mode.
• the second transformation element 22 is arranged for transforming the first polarization mode of the first optical signal (provided by the output of the first polarized SOA 8 2 of the second amplification stage 3 2 ) in the second polarization mode. So, it is located after the first polarized SOA 8 2 . It should be understood that this transformation consists in a rotation from the first polarization mode to the second polarization mode.
• Such an embodiment allows the first combination element 5 to combine the first optical signal (amplified and having the second polarization mode) with the second optical signal (amplified and having the first polarization mode) to produce the output optical signal S ou t- [56]
• the first transformation element 21 and/or the second transformation element 22 comprise(s) a waveplate arranged for inducing the above mentioned polarization mode rotations. These waveplates may be used when the above mentioned free spaces are defined.
• the intermediate processing stage 4 must further comprise third 23 and fourth 24 transformation elements.
• the third transformation element 23 is arranged for transforming the first polarization mode of the first optical signal in the second polarization mode before the second combination element 14.
• the fourth transformation element 24 is arranged for transforming the second polarization mode of the second optical signal in the first polarization mode after the second output of the second splitting element 1 5.
• the third transformation element 23 and/or the fourth transformation element 24 comprise(s) a waveplate arranged for inducing the above mentioned polarization mode rotations. These waveplates may be used when free spaces are defined.
• the amplification device 1 may comprise at least first 29, and second 30, extracting elements and first 33, and second 34, photodiodes.
• Each first extracting element 29, is arranged for taking a first predefined percentage of the power of the first optical signal before a corresponding first polarized SOA 8,.
• Each first photodiode 33 is arranged for producing a first information PM , representative of the power taken from the first optical signal before the corresponding first polarized SOA 8, for the control means 6.
• Each second extracting element 30, is arranged for taking a second predefined percentage of the power of the second optical signal before the corresponding second polarized SOA 9,.
• Each second photodiode 34 is arranged for producing a second information PI2, representative of the power taken from the second optical signal before the corresponding second polarized SOA 9, for the control means 6.
• the first and second predefined percentages may be equal to 1 %. But other values may be used.
• the first 29, and second 30, extracting elements may each comprise a tap coupler arranged for reflecting the first or second predefined power percentage of the first or second optical signal, and of transmitting the complementary power percentage of the first or second optical signal.
• the first or second predefined percentage is equal to 1 %
• the complementary power percentage is equal to 99%.
• the first 29, and second 30, extracting elements may be beamsplitters, such as semi-reflective plates or partially reflective mirrors. These beamsplitters may be used when the above mentioned free spaces are defined.
• the first 29, and second 30, extracting elements are secured to the small plate (or board) 10.
• the first 33, and second 34, photodiodes may be secured to the same plate or to a subsidiary plate positioned below the first one.
• the first 33, and second 34, photodiodes may exhibit a low bandwidth.
• control means 6 may be advantageously arranged for producing all the driving currents 11 , to 14, as a function also of other information representative of powers of the first and second optical signals after the first 8i and second 9, polarized SOAs of ech amplification stage 3,.
• the amplification device 1 may comprise third 31 , and fourth 32, extracting elements and third 35, and fourth 36, photodiodes.
• Each third extracting element 31 is arranged for taking a third predefined percentage of the power of the first optical signal after the corresponding first polarized SOA 8,.
• Each third photodiode 35 is arranged for producing a third information PI3, representative of the power taken from the first optical signal after the corresponding first polarized SOA 8, for the control means 6.
• Each fourth extracting element 32 is arranged for taking a fourth predefined percentage of the power of the second optical signal after the corresponding second polarized SOA 9,.
• Each fourth photodiode 36 is arranged for producing a fourth information PI4, representative of the power taken from the second optical signal after the corresponding second polarized SOA 9, for the control means 6.
• the third and fourth predefined percentages may be equal to 1 %. But other values may be used.
• the third 31 , and fourth 32, extracting elements may each comprise a tap coupler arranged for reflecting the third or fourth predefined power percentage of the first or second amplified optical signal, and of transmitting the complementary power percentage of the first or second amplified optical signal. In the case where the first or second predefined percentage is equal to 1 %, the complementary power percentage is equal to 99%.
• the third 31 , and fourth 32, extracting elements may be beamsplitters, such as semi-reflective plates or partially reflective mirrors. These beamsplitters may be used when the above mentioned free spaces are defined.
• the third 31 , and fourth 32, extracting elements are secured to the small plate (or board) 10.
• the third 35, and fourth 36, photodiodes may be secured to the same plate or to a subsidiary plate positioned below the first one.
• the third 35, and fourth 36, photodiodes may exhibit a low bandwidth.
• the last embodiment allows the control means 6 to precisely balance output powers from the first 8, and second 9, SOAs of each amplification stage 3, according to the targeted power of the output optical signal S out of the amplification device 1 .
• this targeted power is set in the control means 6 through the control plane or a manual setting at startup, each optical path should transmit half of this targeted power. So, the control means 6 adjusts all the driving currents 11 , to I4, accordingly.
• the control means 6 may, for instance, determine the driving currents 11 , to I4, from stored data establishing a correspondence between information representative of powers and driving currents.
• the control means 6 finely tunes each driving current 11 , to I4, to reach the targeted power, while taking into account a tolerance on the targeted power.
• the amplification device 1 may further comprise a polarization dependent optical isolator before each input and/or after each output of each amplification stage 3,.
• the capacity of a WDM transmission system may be approximately tripled and a management of the gain flatness can be performed.
• the invention also allows to compensate lumped losses in optical networks by means of simple management rules.

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• Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

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• 2015
  • 2015-09-25 EP EP15306493.6A patent/EP3148100B1/de not_active Not-in-force
• 2016
  • 2016-09-23 EP EP16770762.9A patent/EP3353909B1/de active Active
  • 2016-09-23 CN CN201680065274.6A patent/CN108352902A/zh active Pending
  • 2016-09-23 WO PCT/EP2016/072773 patent/WO2017051018A1/en not_active Ceased
• 2018
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